FredR

OK chaps-thinking hats on... my 928 started up today just fine after sitting for over a week whilst I was back in te UK. Ran it for about 15 minutes and parked up at my friend's valetting business. After about an hour tried to start it and it would not fire.

Figured I may have wet the plugs so let it stand for a few minutes- cranked it but no sign of life. Hmmm! Could not smell any obvious abundance of fuel- pulled the plugs out of bsank 5/8 and all of them were just fine, no soot, no signs of petrol wetting. Put the lead on one of the plugs- cranked the motor- it sparked.

I went to the back of the car squatted under the rear passenger side and asked my friend to crank turn th eignition key to the on position- as he did this I could hear the fuel pump whirr briefly and stop- normaol behaviour I understand.

Figured if the LH had gone that would not have happened but went home, p-icked up my spare LH and stuck it in the car- no difference. Checked the fuel pump fuse- seemed OK swapped another 53 relay for the fuel pump positioned one- no difference.

Not convinced what the problem culd be here the only things I can think of now are:

1. CPS.
2. Temp 2 sensor?

What am I missing here and is there an easy way to tell if it is the CPS that has a fault? Not sure if ST2 can diagnose that but will have a look in the manual.

Thoughts appreciated - what a PITA this is.

Regards

Fred

Mrmerlin

replace the fuel pump fuse.

Add a battery jumper cable to the neg terminal and then to the shock mounting bolt,
see if the car starts , if so then ground cable had bad connection, or needs to be replaced.

Clean the 14 pin connector under the hood fit a hot post cover if you dont have one.

Pull the vacuum lines off the dampers and FPR, smell for fuel
if any are leaking then replace all 3 of these parts.

Since you have spark the CPS is working, but may be on the way out.
However have you ever done an intake refresh?
maybe its time to do this and replace the knock sensors CPS and hall sensor,
as well all of the other hoses and connectors under the intake.

Finally hold the pedal to the floor and crank it for 30 seconds till it starts

PHIL928

Did you try and give it some gas while cranking it?

Fuel - can you hear the injectors while cranking?
Air - ICV might be seized shut, so not getting any air to start?
Spark - checked!

siscogts

fuel pump gone , imho...
Francesco

John Speake

As Stan says, if you have spark (check from both distributors) then the CPS, EZK and EZK relay are OK.

Replace LH relay with known good one to eliminate for fault finding.

You could do the fuel flow test as per WSM, disconnect return to tank and extend safely into a container, bridge FP relay (get the right pins or you can damage the LH ECU ) run FP for 30 secs and you should collect about 1350cc.

Check 2 smaller red leads to battery +ve are tight.

WallyP

The fuel pump should buzz as the engine spins. No buzz, no start.

If the fuel pump is working, sounds like the injectors aren't injecting...

Quick test - use a stethoscope to listen to an injector while someone spins the starter. You should hear a steady clicking as the engine spins.

If you don't have a stethoscope, try a 1.5m piece of rubber or plastic tubing.

If no clicking, swap the LH relay as a first effort.

FredR

Thanks for the thoughts to date. To addres some of the comments:

1. Inlet manifold was off a few weeks ago to replace some items. Others checked and apparently in god condition.
3. Recent check on the three fuel conrollers/dampers revealed no leaking fuel.
4. There is a cover on the hot post.
5. The fuel pump has an initial buzz on switching on the ignition- need to check during cranking.
6. I have a stethoscope to lsiten to the injectors.
7. Will put ST2 on tomorrow to check temp2 sensor. There could be a failure on one of the knock sensors due to damage on the outer connector- ST2 will show whether this is working or not but even so, should not cause a no start problem?
8. The fuel pump fuse was visually OK-if blown the pump should not have buzzzed at all. Will double check electrical continuity with multi meter. I may try to run the fuel pump with hot wires just to prove it is not the problem.

Regards

Fred

Mrmerlin

replace the fuel pump fuse, with another fuse, dont look at it

FredR

Stan,

No possibility discounted until such itme as it is running again.

Regards

Fred

Bill51sdr

As suggested above, swap out the LH relay first & see if it starts. It is easy to do and they do go bad. It's one of the '53' relays.

FredR

Wally,

I'll be checking the LH relay first thing tomorrow- if the LH relay was down would my pump run briefly when the ignition is switched on as it does?

Regards

Fred

wds928

I just had the same issue. Checked and replaced fuel pump fuse and relay, relay X and ignition relay.

Then cranked the engine with the pedal floored. Fired up after 10 seconds. Looked at the dash and the fuel gauge shows almost empty. I'll add about 4 gallons from the Mercedes and check again. I think fuel level for me was too low. Really dumb!!

FredR

The plot develops....

Went back to my 928 this morning with freshly charged battery. Installed the thing, cranked the motor and and she fired up. Immediately got two alarms- one that the anti lock braking system was off and one I have never seen before with the alarm seemingly about the battery. Strange as the battery was tested last night after charging and everything indicated OK.

Took a look at the voltmeter and it was showing something around 11 volts and no movement on the needle. Hmm.. alternator/diode failure? Not sure this would explain why my motor would not start yesterday.

Cannot see any obvious fuses or relays to check on this one from the siring diagram but if any of you chaps over the pond are still wide aware and full of bright ideas/suggestions do le tme know. I am rather suspecting an alternator failure [I have a couple of spares if they work].

How this links up ot what I saw yesterday is beyond me at the moment.

Regards

Fred

Mrmerlin

what it the charge rate at the hot post and 1500 RPM? SB 13.5 or higher up to 14.2 if lower than 13.5 then indicates a blown diode
is the alternator belt tight? highest load on the belt is just after start at idle.
Have the brushes in the voltage regulator ever been inspected? worn brushes will give an intermittent charge no charge indication

FredR

So, started going through the various tips/suggestions and started with the 14 pin connector as suggested by Stan. Well, what a mess! Upon closer inspection it seemed several of the cables had no insulation.

OK- out with the wiring diagrams and after some analysis of what is connected and what pin assignment is assinged to what, I pulled the connector apart and identified that cables are as per wiring diagram.

The damaged wires from the engine were 1,2,4 [oil pressure sender] & 6 [oil level switch]. Heavens knows what this was doing but no surprise my il pressure indication was not working/had been behaving strangely. Ironic that I just had the dealer fit a new sender from Roger and still it did not work!

I temporarily reconnected these wires up after cutting back to what looked better cable but I suspect these cables need to be replaced. I can only assume something fried these cables.

Re-connected the battery and the motor fired up but the problem with the alternator has not been resolved. The oil pressur eindicator seems to b e working but when I switched off the gauge went to full scale instead of zero.

So, I now need to work out why the alternator is not working, why the anti lock braking system warning light is up as well as sort out any remaining wiring problems.

I suspect I still have some major wiring/electrical issues here. I also wonder what caused these 4 wires to destroy their outer sheath when others around it in the ocnnector seem OK.

Regards

Fred